Westman Islands’ volcanic system comprises 70-80 volcanoes and their
remainders above and below sea level.
It is about 38 km (23 miles) long and 30 km (18 miles) wide.
Between 20 and 30 of those volcanoes were active during Holocene,
and the others during the latter part of Pleistocene. The volcanic
activity of this area probably started during the last 100-200 thousand
years and eruptions during that period have been relatively frequent.
Some of them left submarine craters and crater rows behind,
others islands. During
historical times the volcanic activity has been relatively infrequent,
but unrecorded submarine eruptions most likely took place without people
even noticing them. One
such eruption is mentioned in the proximity of Island Hellisey in a
paper in Reykjavik in 1896 and another in annals from 1637.
The Surtsey Island and Heimaey Island eruptions last century
might confirm the constant activity of the area.
volcanic system follows the same direction as most others of the
country, i.e. southwest-northeast.
A central volcano probably was created during the eruption, which
left most of the Heimaey Island behind.
Earthquakes and tremors indicate a magma chamber at the depth of
10-30 km. Future developments of the system might lead to a land bridge
connecting the archipelago to the mainland.
and a few other spots on the northern part of Island Heimaey can be
traced to the last part of the Ice Age.
Their structure is mainly hyaloclastites (Moberg), but there are
traces of basaltic rock as well.
Alsey and probably Island Hellisey might be about 8,000 years old.
headland Storhofdi on Island Heimaey was
probably created about 6,000 years ago and the Islands Ellidaey and
Bjarnarey are almost equally old.
Heimaey was mostly created 5,200 years ago.
At that time a large crater started very explosively on the sea
floor. A few hills (Saefell)
and the Holy Mountain (Helgafell) were created.
Surtsey was created during the longest historical eruption in
2-3 km long eruptive fissure, partly submarine opened up across the
eastern part of Island Heimaey at two o’clock in the morning of the 23rd
of January 1973. The last
traces of the eruption were noticed on the 26th of July the
eruption, which created this and other islands around it during a period
of a little more than three and a half years, is considered to be among
the longest during historic times.
The eruption was first noticed early in the morning of November
14 1963 some 18 km southwest of the Heimaey Island.
It probably started a few days earlier on the ocean floor, some
130 metres below the surface. It
was very effusive during the time, when seawater had access to the
craters, and on The 15th of November, the island started developing.
At the end of January 1964, the island was 174 metres high.
February another island, Surtur, the younger, started developing.
This eruption ceased next April and the island disappeared
shortly afterwards. Lava
started flowing from the western crater of Surtsey on the 4th of April
1964. Its main flows ran
towards south and east and the lava shield by the crater grew 100 metres
thick. This lava effusion
stopped on the 17th of May in 1965.
At that time the island was 2,4 km² in area.
At the end of May 1965, evidence of another submarine eruption
east north east of Surtsey was seen on the surface.
On the 28th, the island Syrtlingur started developing and the
eruption stopped in October the same year.
This island had disappeared on the 24th of October.
island Jolnir developed 0,9 km southwest of Surtsey during Christmas
1965. This eruption lasted
until the 10th of August 1966 and the island had disappeared at the end
of October the same year. Lava
started flowing again from the eastern craters of Surtsey on the 19th of
August 1966. The flows ran
towards southeast and east until the beginning of June 1967, when the
Surtsey-eruption officially came to an end.
During the period between December 1966 and January 1967, five of
the eastern craters emitted mostly ash and very little lava.
THE SURTSEY ERUPTION had lasted a little more than three years and a half,
when it stopped and the island had grown to 2,7 km² in area. The total volume of tephra was estimated to be 1,1 cubic
kilometres, thereof 60-70% ashes and 30-40% lava. The Westman Island archipelago consists mostly of islands
created the same way. Erosion
has demanded its toll of the Surtsey Island and eventually only one
cliff is going to remain in the ocean.
The island was immediately declared inviolate for the scientists
to explore and up to this date, it is extremely difficult to get a
permission to land there. It
is, however, possible to sail around the island and watch it from the
eruption started at 02:00 o’clock on the 23rd of January
1973 and lasted for 155 days. The
latest signs of it were noticed in the crater Eldfell (Fire Mountain) on
the 26th of July. The
volcanic fissure on dry land was originally 1½ km (1 mile) long and
situated about 300 m (1,000 feet) to the east of the houses in town.
The winds were blowing from the west during the first night and
day, which made it both easier and safer to evacuate the population, as
the ashes were carried away. On
the 25th and 27th of January, easterly winds
carried the ash plume over the town and many houses were totally buried
and others caught fire. Gradually
the activity of the fissure was concentrated within a 200 m area, where
the crater “The Fire Mountain” was created and reached the height of
only pre-warnings of a pending eruption were two waves of earthquakes
and no one connected them with what was to come.
During the first days the northern part of the fissure, closest
to town, was most active and the lava flow reached about 100 m³/sec.
The plume reached the height of 9 km and was clearly visible from
the capital area and elsewhere. The lava flow threatened to close the entrance of the harbour
and on the 6th of February powerful pumps started pumping
seawater on the lava’s edge. This
had never been tried before and it probably saved quite a few houses and
the harbour entrance. The
maximum output of the pumps reached 2,000 l/sec.
majority of the population of Island Heimaey was evacuated during the
first night and day and in the wake of that all kinds of relief work
started. The Icelandic and
foreign governments and individuals spent and donated billions of
Icelandic kronur for that purpose.
The damage was, however, much greater than all that money could
reimburse. At the beginning
of the eruption about 5,300 people lived on the island and
on December 1st 2007 their number was about 4.070.